PNS (tutorial) Flashcards
What is the PNS comprised of?
DRG - Dorsal Root Ganglion (the connection between the spinal cord and the muscles / sensory receptors)
Nerves + ganglia (outside of the brain and spinal cord)
What signal / information comes into the dorsal root of the spinal cord?
And what signal / information comes into the ventral?
Sensory
Motor
What is the plexus?
Spinal nerves
What are the 5 major plexuses?
Cervical
Brachial
Lumbar
Sacral
Coccygeal
How many nerves innervate to one part of the skin?
Many (not just one)
What causes total sensory loss? Will cutting off one nerve that goes to that part of the body causes total sensory loss?
Cut off all nerves that innervate to that area to lose total sensation
No
What is a dermatome?
An area of skin that is supplied by a single spinal nerve
What happens if the dorsal root muscles are cut off?
Muscle weakness, sometimes eventually losing total muscle movement
Which of the plexuses is more protected and least likely to be affected?
Lumbar-sacral plexus
Where do the nerves that go in from L5 - S1 innervate from?
Big toe / feet
How to test for lumbar discopathy?
Stretch raise test
Ask patient to lie down, stretch out leg and raise it - see if they get any pain
Can the PNS regenerate?
Yes to a certain extent
Why is decompression surgery then useful / effective?
Nerves after decompression can get better
Name the labels A-D on this diagram:
A = Dorsal Root B = Dorsal Root Ganglion C = Plexus (spinal nerves) D = Ventral Root
What are the consequences if there were lesions at V-Z?
Suggest common medical scenarios which might result in a lesion occurring at each point.
V - sensation loss
W - Muscle weakness (not total loss of motor function)
X - Similar effects as cutting off at V and W, as it is cutting off at the part where those 2 roots merge?
Y - Loss of sensation from the muscle?
Z - Loss of motor function to the muscle
Strain injury
Prolapse disc - V and W lesions (causes loss of sensation or muscle weakness)
Trauma, peripheral neuropathy - Y and Z lesions
Lumbar plexus least likely to be affected
50M - Has pain in his right leg. He reports that it extends from his buttock, down his thigh, calf and into his toes and that it gets worse when he moves. He describes the pain as stabbing, burning or shooting and has pins and needles in his right leg. He says that he feels as though his right leg is weaker than the left.
- Which structures are involved to produce the symptoms?
- What is the name of the condition?
- What could be the cause of the condition?
- What treatment options are available?
- A mixture of the lumbar and sacral plexus - L5 and S1 (gluteus maximus? thigh)
Innervates to the feet and big toe - Lumbar-spinal radiculopathy
- Nerve compression (sciatic nerve)
Slip disc
Trauma to the disc
Trauma to the bones = crush your nerves e.g. bone cancer
Arthritis
Piriformis syndrome - muscle that attaches the femur to the top of the pelvis can trap the nerve and compress it - Stretch-raise test can be used to diagnose - if they feel any pain while laying down, stretching out their leg and trying to raise it
Physiotherapy, ibuprofen (if the pain it too high), injections i.e. epidural to the sacral portion, decompression surgery - discectomy (replacing the disc and clearing the compression)
